File: sfinae4.C

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gcc-riscv64-unknown-elf 8.3.0.2019.08%2Bdfsg-1
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// { dg-do compile { target c++11 } }

namespace std { template <class T> T&& declval(); }

template<typename _Tp, typename... _Args>
  class is_constructible_mini
  {
    typedef char __one;
    typedef struct { char __arr[2]; } __two;

    template<typename _Tp1, typename... _Args1>
      static decltype(::new _Tp1(std::declval<_Args1>()...), __one())
      __test(int);

    template<typename, typename...>
      static __two __test(...);

  public:
    static const bool value = sizeof(__test<_Tp, _Args...>(0)) == 1;
  };

static_assert( !is_constructible_mini<int[], int>::value, "");
static_assert( !is_constructible_mini<void, int>::value, "");